The audio system that I’m building requires 2 low-power computers: 1 for the touchscreen controller (not using an iPod Touch for the moment) and 1 to act as a webserver and serial-console server.

Once again eBay has come to the rescue, and by searching for ‘geode’ - a low-power processor for Thin Clients & Small Form Factor (SFF) PCs - I found the 2 machines that I needed. These are the specs:

magnesium (the black one)

• 800 MHz Geode
• 256 MB RAM
• 6 GB CF drive
• Onboard graphics, audio, serial, parallel, USB & 10/100 ethernet

£70 + P&P

potassium (the grey one)

• 300 MHz Geode
• 256 MB RAM
• 6 GB 2.5″ IDE drive
• Onboard graphics, audio, serial x2, parallel, USB & 10/100 ethernet

£35 + P&P

Magnesium is used as the client machine, and potassium runs a custom-made webserver and the control software for the VAMS-0808 Matrix Switcher.

Both came pre-installed with Puppy Linux, a lightweight distribution designed for low-power machines such as these. It runs surprisingly quickly, but to make it easier for me to maintain I decided to install Ubuntu.

On such slow computers it took many hours to get Ubuntu installed on magnesium alone. I initially installed to the CF drive that came with the machine. However I found it to be quite slow, so I followed a guide for running Ubuntu via network boot and removed the CF disk. I did the same for potassium. Both booted off of the fileserver, boron.

Unfortunately during installation, I found that the slower of the machines has a tendancy to overheat causing the machine to hang. To get Ubuntu installed I had to remove the case. This has now been rectified by installing a blower to get at least some air circulating. This is the only fan in either of the machines. Magnesium gets quite hot but has never crashed because of it. It also sits in a cooler environment, and is much better engineered.

Sadly I’ve been forced to install Windows XP on magnesium purely because I couldn’t get the touchscreen to work under linux despite spending more than a day trying to. While it was detected, and it detected touches, the calibration was completely off and there was no way to configure it. Rather than waste any more time I decided to switch to Windows and everything has worked beautifuly since then. To accomplish this I’ve had to reinstall the CF disk since as far as I know XP Pro can’t do diskless booting.

Shots of these computers in use and more information on their roles to come soon.

Thanks to the chip manufacturer of the cheap serial port card, I’ve managed to get some extra serial ports working. If you can’t figure out how to get additional serial ports working, I recommend this guide [ZIP, 792KB] available from the Moschip driver download page. It should be valid for most models of serial cards, and explains how to add more than the standard 4 ports that most linux installs have.

Now that this problem is out of the way I can continue with writing the remote control software for the audio system.

Having put the 4 port serial card back into boron, the onboard port now works again, so I’ll probably continue with developing the software. The expansion card still doesn’t work though, so I’ve ordered a cheap 2-port card from eBay in the hope that a different card will work.

Before reinstalling the card I upgraded Ubuntu to see if that would help (it didn’t) which brought its own scary moment of the 1TB RAID volume being dead. That too is solved now - the drive letter assignments had changed.

Several months ago I posted some information on the cable to connect a Compaq T2400h to a standard serial port. This weekend I finally got around to trying out the information that I found. I now have the 2.4KVA UPS at the bottom of my rack cabinet talking to my Ubuntu-based fileserver, boron.

The first step was to create the cable. This requires a 9 pin female ‘D’ connector and a matching male connector. For the cable I used an offcut of CAT5, though normally serial cables do not use twisted pair (usually just parallel wires).

The software part is done using NUT, for which there is a package included in the Ubuntu distribution. This software talks to the UPS, monitors it’s status and allows other computers to check the status. The monitoring applications are then responsible for shutting down the computers attached to the UPS should power fail and the battery become critical. So far this is just boron and my Windows machine, aluminium. The latter uses WinNUT to shut down Windows when needed.

There were a few problems getting NUT to work with Ubuntu. First off, the package doesnt put any configuration files in the /etc/nut path, so I had to go hunt for the examples and copy then modify them. The next problem was with permissions for the serial port. For testing purposes I tried running the protocol module as root, but this introduced different permissions problems. The solution was to add the ‘nut’ user to the ‘dialout’ group, which is one group that has access to the serial ports. To my relief this got everything working.

These are the parameters that I can access over the serial connection:

simon@boron:~$ upsc compaq@boron
battery.charge: 97.22
battery.runtime: 1620.000
battery.voltage: 0055.50
battery.voltage.nominal: 0048.00
driver.name: upscode2
driver.parameter.input_timeout: 5
driver.parameter.manufacturer: Compaq
driver.parameter.port: /dev/ttyS0
driver.parameter.use_pre_lf: yes
driver.version: 2.0.5
driver.version.internal: 0.84
input.voltage: 0244.50
input.voltage.maximum: 0276.00
input.voltage.minimim: 0162.00
input.voltage.nominal: 0230.00
output.current: 0001.95
output.frequency: 0050.00
output.voltage: 0215.10
ups.alarm:
ups.delay.reboot: 000
ups.delay.shutdown: 000
ups.load: 21.875
ups.mfr: Compaq
ups.model: UPS 2400 VA FW -0023
ups.power.nominal: 2300.000
ups.serial: E########
ups.status: OL TRIM

These are the resources that I used to get the UPS/NUT combo working:

• [Nut-upsuser] Compaq T2400H UPS model 242688-006
• Network UPS Tools (NUT) on Ubuntu

Boron has been running Fedora since it was intitally built several years ago. It has suffered from frequent problems all the time it has been in use, and recently I gave up and have gone for something more solid and stable - Ubuntu.

(more…)

A little over two weeks ago I ordered a new computer from EfficientPC. They appear to be the only independent business selling true linux-based machines. Anyway, what I was after was a box that could run MythTV reliably but quietly (since it will be in the living room).

At our previous house I tried to set up Boron as the machine for this job, since we had the space under the TV (though I had to take a jigsaw to the back of the cabinet) and it was the only suitable machine for the job at the time. Our huge and heavy CRT (now retired to the master bedroom) has component input, so I tried several DVI to component converters that supposedly worked on the Radeon 9600 that sits inside Boron. As these things always go, it didn’t work. So now that we have a TFT TV with VGA input, I have another chance to get a fully-functional media server set up.

This new machine is pretty much silent - certainly quiet enough to sit in the living room, behind the TV (it’s also very slim). I’ve also discovered that it’s pretty nippy, sporting an Intel Core 2 Duo E2140 with just 512MB of DDR2 (since there doesnt need to be a huge amount of RAM for a media centre - processing power is more important). The 500 GB drive should give a few hundred hours of recording capacity. It has been called Sodium, because I try to go for things that are orangey with the Ubunto machines - sodium lamps shine orange - and it will be the ‘Master Backend’ server for MythTV. Boron will be a slave server, and there will be various front-ends around the house.

I found out after ordering this new Asus Camulus-based computer that EfficientPC is run by a single person, so service is not speedy. He is apparently struggling to keep up with demand, so emails often go unanswered. I am not bothered by this, and the quality of the product is pretty good. This guy makes sure that the hardware that he provides works with Ubuntu, which provides more peace-of-mind than if I would have ordered the parts myself then found out that they don’t work under linux.

The only problem, other than breaking a PSU, is that the PCI DVB-T tuner cards that I have will not fit inside the Isis case. I’ve ordered a Nova-T 500 dual tuner card to compensate (along side the replacement PSU and another 500 GB drive). The beauty of MythTV is that it will allow me to use all of the cards in separate machines, combined into one set of recordings that can be watched through any of the MythTV front-ends in the house. So that’s 4 tuners allowing 4 shows to be recorded simultaneously. Eventually this may be expanded to include satellite tuners because we have a very weak digital signal around here. More on the specifics of MythTV and how it’s being set up in our house soon.

There will be photos shortly, once I’ve got the system fully set up.